U.S. Pat. Nos. 4,812,247 and 4,812,248 of William Kohut describe a stable ball clay slurry that contained from about 50 to about 65 weight percent (by weight of dry ball clay) of silica. In the “comparative examples” discussed in such patents (see, e.g., comparative examples 10–89 of U.S. Pat. No. 4,812,427, at columns 39 et seq.), a discussion was presented of certain slurries made from clays with a silica content of 72 weight percent. Referring to columns 43 and 44 of U.S. Pat. No. 4,812,427, and in the examples 16, 17, 18, and 19 thereof, slurries made from clays containing 72 weight percent of silica were unstable, having a settling index of 0.11, 0.18, 0.16, and 0.18, respectively. By comparison, the stable ball clay slurry of U.S. Pat. No. 4,812,427 had a settling index of at least 0.9; but the maximum allowable silica content for such slurry was 65 percent. It is an object of this invention to make a clay slurry with a silica content of at least 68 percent wherein such slurry is stable and has properties suitable for slip casting.